Like a jeweler assessing a diamond ring or a doctor checking for swollen tonsils, Patterson squinted and peered at one coneflower leaf after another, followed by intense note taking. Patterson, along with a dozen other high school interns, was tracking the gradual demise of the coneflower leaves from air pollution, namely ozone. The fledgling scientists were working at the Appalachian Highlands Science Learning Center in the Great Smoky Mountains National Park.
Plants suffering from ozone have a distinct look, a yellowing of the leaves unlike that caused by natural leaf demise or disease.
“It’s partly knowing what to look for,” said Patterson. “If you do it enough you just say, ‘That’s ozone.’”
In the early 1990s, a group of researchers in the park put plants in gas chambers, subjected them to ozone and studied the results. In the process, they nailed down the specific symptoms of ozone-instigated leaf damage.
One of the research leaders, Howard Neufeld of Appalachian State University, took that experiment to the field to study the effects of ozone on plants in their natural environment. The Appalachian Science Learning Center, a research outpost in the Haywood County portion of the Great Smoky Mountains National Park, helped Neufeld plant a plot of coneflowers and enlisted high school interns to monitor the plot, known simply as the “ozone garden.”
As the summer progresses, students track individual leaves as they turn yellow, then crinkly, and eventually fall off, explained Park Ranger Susan Sachs, who operates the Appalachian Highlands Science Learning Center.
On a recent summer afternoon while the interns were diligently inspecting the garden, Sachs unlocked a shed where a computer monitors hourly ozone levels. It showed a whopping 77, pushing closer toward an orange alert as the afternoon wore on.
That same ozone causing the cut-leaf coneflowers (Rudbeckia laciniata) to yellow and crinkle is floating through the air Sachs and the interns are breathing.
“When it is code orange — or even a day like today when it’s borderline code orange — I’ll still go outside, but I won’t do a lot of physical exertion like go hiking,” Sachs said.
Plants and ozone
Like humans, plants also breathe. They have tiny pores on their leaves that open to inhale carbon dioxide. But that’s not all they inhale.
“If you bring CO2 in, it brings in ozone as well,” explained Neufeld.
Plants suffering from ozone damage don’t grow as well, stunted by up to 6 percent in their annual growth. Ozone crop losses amount to about $3 billion a year, Neufeld said.
Neufeld, in cooperation with several other scientists, researched the nutrition value of plants suffering from ozone. Plants showing signs of ozone damage had decreased nutrient value.
Neufeld has also studied the connection between ozone damage and seed production. Park Ranger Joy Absher, stationed at the Appalachian Highlands Science Learning Center, is collecting coneflower seed pods for Neufeld. Given the dozens of tiny seeds that form on each flower head, collecting the little buggers is a bit tricky, however.
Before the flower heads go to seed, the staff put nylon bags over the flower.
“Any seeds that fall out, fall out in the bag,” Sachs said. It also keeps birds from eating them. When the seeds have developed, they clip the stem of the flower, nylon baggie and all. When it dries, they remove the bag, dump out the seeds and start counting.
The research is only in its second year, but so far it appears plants with ozone damage produce about half as many seeds.
During his 20 years of ozone research on plants, Neufeld noticed two plants of the same species growing side-by-side reacted differently to ozone. After several years of research, Neufeld found it boils down to genetic variations within plants.
It seems like good news that some plants could have a natural immunity to ozone, but Neufeld doesn’t see it that way. Remember the seed research? Plants that don’t cope well with ozone pass on fewer seeds, allowing plants that cope better to dominate the seed gene pool.
“If you reduce the genetic diversity, you put that plant species at risk,” Neufeld said.
Just like with people, genetic diversity means some plants within a species will be more or less susceptible to certain diseases — a few likely immune. If a disease sweeps through, genetic diversity keeps it from killing off an entire species. Genetic diversity means some plants can tolerate drought better, or various other environmental factors. Loss of genetic diversity puts a species’ long-term survival at risk, and ozone could do that to plants.
“It’s a hidden problem because you can’t see genetic diversity,” Neufeld said.
But there’s another potential concern over ozone damage to plants. Remember those pores on a plant’s leaves? When they open their pores to breathe, water escapes out of their leaves.
“They are like a giant wick sucking water out of the soil and transporting moisture into the sky,” Neufeld said. That moisture forms into clouds, which rain back down on the earth. In a drought, plants don’t have much water to spare so they clam up their pores and stop breathing so they don’t lose as much water through their leaves. There is some indication that high levels of ozone paralyze the pores, called stomates. If they don’t open and close properly, it can throw off the hydrological cycle, Neufeld said.
The Smokies is one of only five sites in the nation using plants to monitor ozone.
Neufeld’s research this summer would not be possible if not for the team of high school interns stationed at the Appalachian Highlands Science Learning Center to monitor the ozone garden. A Burroughs Welcome Fund science grant pays for the high school intern program, now in its fourth year. The Friends of the Smokies secured the grant on behalf of the park service.
“They are interested in getting kids interested in science, and they see the National Park Service as a good community resource for linking students with scientists,” Sachs said.